Injection molding is a molding method whereby a plastic material is fluidized by a melting process and injected into a mold. The commonly used injection molding machine for performing injection molding is a hydraulic injection molding machine that opens or closes a mold using the hydraulic pressure.
Korean Patent Publication No. 2009-0092494 discloses the structure of an injection molding machine in which a mold is opened or closed by movement of a moving template relative to a fixed template. This injection molding machine is designed such that a piston rod within a cylinder body is coupled to the moving template and can move back and forth, and as the piston rod moves back and forth, the mold is opened or closed.
An example of the injection molding machine is shown in FIGS. 1 and 2 in detail.
FIG. 1 is a diagram showing a clamping apparatus of an injection molding machine according to the related art. Additionally, FIG. 2 is an enlarged diagram of section A of FIG. 1.
As shown in FIGS. 1 and 2, the clamping apparatus 1 of an injection molding machine includes a fixed template 2 and a moving template 3 that is moveable back and forth relative to the fixed template 2. A fixed mold and a moving mold are installed on the inner surface of the fixed template 2 and the moving template 3, respectively.
A bracket 5 of the fixed template is installed on one side of the fixed template 2 to fix the position of a cylinder body 7 into which oil is fed, and a bracket assembly 6 is installed on one side of the moving template 3 to fix the position of a piston rod 4 that can be inserted into the cylinder body 7. The cylinder body 7 and the piston rod 4 may be collectively referred to as a booster cylinder 9.
A flange 8 that is coupled with the bracket 5 by a predetermined fastening element is installed on the outer surface of the cylinder body 7. In detail, the flange 8 has, at the center part, a predetermined hole through which the cylinder body 7 passes. When the cylinder body 7 is inserted into the hole, the flange 8 and the cylinder body 7 are coupled together.
In addition, the flange 8 has a fastening hole 8a into which a predetermined fastening element as a bolt is inserted, and a key hole 8b into which a pin is inserted, formed in the front-rear direction. Also, the bracket 5 has holes corresponding to each of the fastening hole 8a and the key hole 8b. 
The booster cylinder 9 is fixedly coupled to the fixed template 2 as follows. First, an operator fits the booster cylinder 9 having the coupled flange 8 into the bracket 5 of the fixed template. In this instance, the operator aligns the key hole 8b of the flange 8 with the key hole of the bracket 5, and inserts a pin into each key hole to position the flange 8 relative to the bracket 5.
Subsequently, the operator inserts a fastening element such as a bolt into the fastening hole 8a of the flange 8 and the fastening hole of the bracket 5 to couple the flange 8 to the bracket 5. Accordingly, the booster cylinder 9 can be fixedly connected to the fixed template 2.
However, when an operational tolerance occurs in the fit coupling of the booster cylinder 9 to the bracket 5, delicate coupling of the two components is not achieved. Further, in the connection process of the flange 8 and the bracket 5, after the coupling position of the two components is aligned by inserting the pin into the key hole 8b, the two components are coupled by inserting the fastening element into the fastening hole 8a, so the process is very complex and tedious. Even further, the fastening hole 8a and the key hole 8b are too weak to withstand kinetic energy of the piston rod 4 because they run through in the same horizontal direction as the movement direction of the piston rod 4 of the booster cylinder 9.